Prostaglandin D.sub.2 is a natural prostaglandin occurring in many organs, but above all in the brain and performing a large number of biological functions. However, prostaglandin D.sub.2 as well as analogs of PGD.sub.2 (cf. DOS 2,517,773) are even less stable chemically than the prostaglandins of the E series.
Interest has, therefore, existed in developing chemically stable analogs of the prostaglandin D series having the same or a similar biological activity as PGD.sub.2. Several chemically stable 11.alpha.- and 11.beta.-fluoro- or -chloro-derivatives of 9.alpha.,15.alpha.-dihydroxy-5-cis-13-trans-prostanoic acid have been described in chemical literature [E. Arroniz et al., Prostaglandins 16:47 (1978)]; however, apart from relatively weak bronchodilatory properties of the 11.alpha.-fluoro-derivative, this publication neither discusses biological data nor does it disclose the synthesis of other 11-haloprostanoic acid analogs.